1. Field of the Invention
This invention relates to a dispersant for drilling fluids or muds which can be used at high temperatures.
2. Description of the Previous Drilling Fluids
Clay slurries such as water-based bentonite clay slurries are used as drilling fluids. To disperse the solid materials, a dispersant such as ferrochrome lignosulfonate (FCLS) has been used. However, when these FCLS containing slurries are used at higher temperatures such as above 250.degree. F., FCLS breaks down and the drilling fluid gels.
Another dispersant system which has been used with drilling fluids is a combination of the FCLS and Mil-Temp which is a sulfonated polystyrene maleic anhydride copolymer made by Milchem, a subsidiary of Baker International. This system requires two components, it requires the renewed maintenance of the FCLS and it is more expensive than just FCLS in view of the higher cost of the added Mil-Temp.
3. Objects of the Invention
It is an object of this invention to obtain a dispersant for water-based drilling fluids which remains operable even at high temperatures such as up to 450.degree. F.
It is a further object of this invention to obtain a drilling fluid with a dispersant which remains operable at high temperatures.
It is a further object of this invention to be able to drill down into an earth formation at significant depths where the drilling temperatures are high such as above 350.degree. F. by using a water-based clay drilling fluid having a dispersant which remains stable at this higher temperature.
These and further objects will become apparent as the description of the invention proceeds.